You fail to address the fact that until humans began introducing alternative forms of radiation into the world the only natural radiation source was cosmic rays aka background radiation.

Quoting: Plasmare

You have absolutely no idea what you're talking about. There are numerous sources of ionizing radiation even if we leave out the Sun. There are radioactive elements in the Earths crust, there is radon, there are CONTINUOUS leakages of particle radiation from the Sun reaching the earths surface. (Take a ginger counter and point the fucking probe slots towards the Sun and see what you get!